Severe is not appropriate.

"Sever" is most Appropriate

strategy/src/main/java/com/iluwatar/strategy/MeleeStrategy.java

@@ -31,6 +31,6 @@ public class MeleeStrategy implements DragonSlayingStrategy {
 
   @Override
   public void execute() {
-    System.out.println("With your Excalibur you severe the dragon's head!");
+    System.out.println("With your Excalibur you sever the dragon's head!");
   }
 }